Ester production



United States Patent 3,397,227 ESTER PRODUCTION Igor Sobolev, Grinda,Calif., assignor to Shell Oil Cornpany, New York, N.Y., a corporation ofDeiaware No Drawing. Continuation-impart of application Ser. No.405,858, Oct. 22, 1964. This application Nov. 9, 1967, Ser.'N0. 681,932

11 Claims. (Cl. 250-486) ABSTRACT OF THE DISCLOSURE Reaction of acyclichydrocarbon monoalkene monocarboxylic acid, epihalohydrin and areaction-limiting amount of trialkylamine produces2-hydroxy-3-alkenoyloxypropyltrialkylammonium halide, useful in theproduction of polymeric wet end additives.

CROSS-REFERENCE TO RELATED APPLICATION This application is acontinua-tiondn-part of applicants copending application Ser. No.405,858, filed Oct. 22, 1964, now abandoned.

BACKGROUND OF THE INVENTION Compounds incorporating quaternary nitrogenatoms and ester linkages within the molecule are known in the art, beingproduced, for example, by acylation of ethanolamine derivatives. Suchmaterials have established utility as surface active agents and thelike, particularly when the acid moiety of the cationic acid is derivedfrom a long-chain alkanoic acid. In part because of the method ofproduction, it is difficult to prepare esters of this type withadditional reactive functional groups, and in general, the cationicesters of the art contain only the ester linkage and the quaternaryammonium moiety as active reaction sites. In the U.S. Patent 3,329,706,issued July 4, 1967, to Sobolev, there is described a process for theproduction of cationic esters containing a free hydroxyl group and alsoethylenic unsaturation. Such esters are characterized as2-hydroxy-3-alkenoyloxy-propyltrialkylammonium halides and are preparedfrom reaction of the free acid and a glycidyltrialkylammonium halide.Although this process offers a method for the production of suchcationic esters in high yield and purity, it does require thepre-formation of the glycidyltrialkylammonium halide. It would be ofadvantage to provide a'method for the production of these cationicesters from simpler and more readily available starting materials.

SUMMARY OF THE INVENTION It has now been found that an improved processof producing 2-hydroxy-3-alkenoyloxypropyl-trialkylammonium halidescomprises the process of directly reacting an alkenoic acid, anepoxyhaloalkane and a tertiary amine in an inert polar solvent. Incontrast with somewhat related processes of the prior art, the successof the present process is determined by the use of selected reactantratios, without the use-of which little production, or at least asubstantially lessened production, of the desired cationic ester isobserved.

DESCRIPTION OF PREFERRED EMBODIMENTS The alkenoic acid employed in theprocess of the invention is a hydrocarbon carboxylic acid possessing atleast one canboxy group and at least one e-thylenic link- 3,397,227Patented Aug. 13, 1968 age, i.e., non-aromatic carbon-carbon doublebond, which ethylenic linkage(s) constitutes the only carbon-carbonunsazturation present within the molecule. Preferred acids are acycliclower monoalkene monocarboxylic acids con,- taining from 3 to- 8 canbonatoms, especially those acids wherein the ethylenic linkage isconjugated with the carboxy group. Thus, lower monoalkene monocarboxylicacids such as cr-otonic acid, 3-b-uten0ic acid, S-hexenoic acid,5-methyl-6-heptenoic acid and the like are operable in the process ofthe invention. Best results areobtained, however, when the ethyleniclinkage, in addition to being conjugated with the carboxy group, is alsoterminal. One class of acids of this type is represented by the formulaCH2=CCO2H wherein a is a whole number from O to 5 inclusive. Thesea-(nonto monoalkyl)acrylic acids are illustrated by acrylic acid,methacrylic acid, ethacrylic acid and a-amylacrylic acid. A particularlypreferred class of lower monoalkene monocarboxylic acids, principallybecause of the desirable properties of the products produced therefrom,comprises acrylic acid and methacrylic acid, generically designated(meth)acrylic acid.

The tertiary amine reactant comprises a trivalent nitrogen atom, eachvalence of which is satisfied with an alkyl substituent of from 1 to 20carbon atoms. Such amines are represented by the formula NR wherein eachR group independently is alkyl of from 1 to 20 carbon atoms. Preferredtertiary amines have at least two, and more preferably three, loweralkyl substituents, that is, alkyl of from 1 to 4 carbon atoms, and bestresults are obtained When the nitrogen atom of the tertiary aminepossesses at least two methyl SllllJStltLlCl'liS. Suitable aminereactants include trimethylarnine, triethylamine, tributylamine,dimethyloctylarnine, diethyldecylamine, dimethyllaurylamine,dimethylstearylamine, dibutyltridecylamine, methylamyldecylam-ine,trilaurylamine and the like.

The epoxyhaloalkane is an m,n-epoxy-o-haloalkane wherein m, n and 0represent adjacent atoms in a continuous carbon chain. Althoughepoxyhaloalkanes of greater chain length are operable, the preferredepoxyhaloalkanes comprise the epihalohydrins, that is, the2,3-epoxy-1-halopropanes. The halogen moiety of the epihalohydrinreactant is suitably fluorine, chlorine, bromine or iodine, although thepreferred epihalohydrins are those wherein the atomic number of thehalogen is from 17 to 35, Le, the middle halogens chlorine and bromine,and particularly preferred as the epoxyhaloalkane reactant isepichlorohydrin.

It has been found that the ratio of reactants present in the reactionmixture exerts a substantial influence upon the conversion of reactantsand the yield of the desired2-hydroxy-3-alkenoyloxypropyltrialkylammonium halide. The stoichiometryof the reaction process would predict the desirability of employingequimolar amounts of each of the three reactants. However, whenequimolar amounts of reactants are employed, reduced yields of thedesired cationic ester product are obtained. The relative molar amountsof alkenoic acid and epoxyhaloalkane does not appear to be critical, andmolarratios of alkenoic acid to epoxyhaloalkane from about 3:1 to about1:3 are satisfactorily utilized. Generally, no great excess of eitherthe alkenoic acid .or the epoxyhaloalkane is required and no substantialadvantage is gained by the use thereof. Molar ratios of alkenoic acid toepoxyhaloalkane that are substantially stoichiometric, that is, ratiosfrom about 1.521 to about 1:15 are preferred. It is highly desirable,however, to employ a reaction-limiting amount, i.e., an amount less thanthe stoichiometric amount, of the trialkylamine reactant in order toobtain the optimum yield of the desired cationic ester product, and thenumber of moles of trialkylamine per mole of limiting other reactant,that is, mole of alkenoic acid or mole of epoxyhaloalkane, whichever issmaller, should desirably not exceed about 0.95. The use of less thanstoichiometric amounts of the amine reactant results, of course, inincomplete conversion of the alkenoic acid and epoxyhaloalkane, butthese reactants may be recovered and recycled to improve the overallconversion. Although the selectivity for production of the desiredcationic ester not infrequently increases with lessened proportions ofthe trialkylamine, the use of too small an amount of trialkylaminerelative to the other reactants unnecessarily increases the operatingexpense, because of the required increase in recycle operation, withoutobtaining any compensating advantage. From practical considerations, therelative amount of trialkylamine should be at least about 0.5 mole permole of limiting other reactant. Relative amounts of trialkylamine fromabout 0.5 mole to 0.85 mole, especially amounts from about 0.6 mole toabout 0.8 mole, per mole of limiting other reactant are satisfactory.

The process of the invention is conducted in liquid phase solution in aninert polar solvent. Suitable solvents are liquid at reactiontemperature and pressure, are capable of dissolving the reactants andare inert to the reactants as well as the products produced therefrom.Illustrative solvents include sulfones such as dimethyl sulfone andsulfolane; N,N-disubstituted lower alkyl amides, e.g., dimethylformamideand N,N-dimethylacetamide; and sulfoxides such as dimethylsulfoxide.Preferred solvents, however, largely for economic reasons, comprisecertain alcohols. It has been found that primary alcohols, such asmethanol and ethanol, are not inert and are therefore not satisfactoryas solvents in the present process, apparently because of a promotion oftrans-esterification processes leading to substantially decreased yieldof the desired cationic ester. However, when the alcohol possesses atleast two non-hydrogen substituents on the carbon to which the hydroxylgroup is attached, that is, the alcohol is a secondary or a tertiaryalcohol, such trans-esterification processes do not take placeextensively and high yields of the desired product are obtained. Thepreferred alcohol solvents therefore comprise a carbon atom to which isattached one hydroxyl group and from two to three hydrocarbylsubstituents which are alkyl of from 1 to -6 carbon atoms or are aryl of6 carbons, i.e., phenyl, and any unsatisfied valences of the centralcarbon atom are satisfied by hydrogen substituents. Such alcohols,characterized as dito trihydrocarbyl carbinols wherein the hydrocarbylsubstituents are :as defined above, preferably have from 3 to 10 carbonatoms and are illustrated by isopropanol, secbutanol, tert-butanol,tert-amyl alcohol, triethylcarbinol, dimethyl phenyl carbinol and methylethyl phenyl carbinol. More preferred are the dito trialkyl carbinolswherein the alkyls are alkyl of 1 to 6 carbon atoms and particularlypreferred are the dito trialkyl carbinols having a total of from threeto four carbon atoms, i.e., sec-butanol, tert-butanol and isopropanol.The alcohols employed as solvents are preferably substantiallyanhydrous, as the presence of water appears to be detrimental to thereaction process. The presence of small amounts of water, e.g., up toabout of the reaction mixture, may be tolerated without losing theadvantages of the invention, but the yield of desired cationic esterwill be somewhat lowered.

The method of mixing the reactants and solvent is not critical. Althoughit is frequently desirable to maintain the concentration of thetrialkylamine reactant at a minimum, as by adding the amine inincrements to a mixture of the other reactants and solvent, it is alsosuitable to initially mix the entire amount of reactants and solvent.The reaction is preferably conducted at somewhat elevated temperatures.Reaction temperatures from about 30 C. to about 125 C. are satisfactory,although reaction temperatures from about 50 C. to about C. arepreferred. The process may be conducted at atmospheric, subatrnosphericor superatmospheric pressure so long as the reactants are maintained inthe liquid phase. Little apparent advantage is gained by the use ofreaction pressures considerably different than atmospheric, and the useof substantially atmospheric reaction pressures, e.g., from about 0.5atmosphere to about 5 atmospheres, is preferred.

It is generally desirable to make some provision in the reactionprocedure for the inhibition of alkenoic acid polymerization,particularly when the alkenoic acid is readily polymerizable, e.g., asacrylic acid, methacrylic acid or the like. Surprisingly, it is notnecessary to rigorously exclude oxygen from the reaction environment andthe process of the invention is conveniently conducted under anatmosphere of air. Prevention of alkenoic acid polymerization iscustomarily accomplished by the inclusion within the reaction mixture ofan inhibitor. Conventional polymerization inhibitors capable of trappingorganic free radicals formed during the reaction process aresatisfactory, provided that the inhibitor is inert toward the reactantsand the products produced therefrom. Preferred inhibitors thereforecontain no active hydrogen atoms. Illustrative of suitable inhibitorsare the quinones, particularly monoto dinuclear quinones, e.g., 1,4-benzoquinone, 1,2-benzoquinone, 1,4-naphthoquinone and a1- kylated orhalogenated, particularly chlorinated, derivatives thereof such aschloranil, duroquinone, 2-ethylbenzoquinone and the like; as well ashindered phenols, i.e., phenols wherein the phenolic hydroxyl group ishindered by the presence of branched alkyl substituents on each ringposition ortho relative to the hydroxyl group. Illustrative of the classof hindered phenolic inhibitors are 2,6- di-tert-butylphenol, 2,6-ditert-butyl-4-methylphenol, 2,6- diisopropylphenol and2,4,6-tri-tertbutylphenol. The inhibitor, if employed, is added incomparably small amounts. Amounts of inhibitor from about 0.001 to about5 molar percent based on the alkenoic acid reactant are suitable, whileamounts from about 0.01 to about 3 molar percent on the same basis arepreferred.

Subsequent to reaction the product is separated and recovered byconventional methods such as precipitation through the addition of anon-solvent, crystallization through a cooling procedure, by selectiveextraction or the like.

The products of the invention are2-hydroxy-3-alkenoyloxypropyltrialkyl-ammonium halides. Illustrative ofsuch products are 2 hydroxy-3-acrylyloxypropyltrimethylammoniumchloride; 2 hydroxy-3-methacrylyloxypropyltrimethylammonium chloride, 2hydroxy-3-ethacrylyloxypropyltrilaurylammonium bromide, 2hydroxy-3-methacrylyloxypropylmethyldibutylammonium chloride and 2-hydroxy-3-(2 ethylacrylyloxy)propyldimethylstearylammonium chloride.

The products of the invention are suitable for use in numerousapplications. As cationic materials they exhibit surface activity andare further useful as biocidal chemicals, particularly germicides. Thenumber and variety of reactive functional groups present allow wideusage as chemical intermediates, wherein, for example, the hydroxylgroup may be esterfied or etherified, other useful quaternary ammoniumsalts prepared by anion exchange, or alternatively the unsaturatedlinkage can be epoxidized to form useful epoxy resin precursors. Aparticularly important utility for the products of the invention is inthe formation of polymeric materials, useful, for example, as wet endadditives in paper manufacture.

To further illustrate the improved process of the invention, thefollowing examples are provided. It should be understood that thedetails thereof are not to be regarded as limitations, as they may bevaried as will be-understood by one skilled in this art.

Example -I r A solution was prepared from 200 gr tert-butyl alcohol, 60g. (0.80 mole) methacrylic acid, and 4g. 2,.6-di-tertbutyl-4-methylphenol inhibitor. The solution was maintained atapproximately C. while gaseous trimethylaminewas bubbled into thesolution until the solution weight had increased 38 g. (which represents0.64rnole of the amine). To the mixture was added 74 g. (0.80 mole) ofepichlorohydrin. A -180 -200ml. aliquot of this solution was placed in aseparate container and shaken for 72 hours while maintained at55' C. Tothe product'mixture, which contained appreciable quantities ofcrystalline precipitate when cooled to room temperature, was added sixtimes its weight of acetone and the product mixture was allowed to standfor one hour. Filtration afforded crystals which were washed withacetone and dried under vacuum at 30-40 C. The yield of2-hydroxy-3-methacrylyloxypropyltrimethylammonium chloride was 66% basedupon the trimethylamine charged.

Example II By procedures similar to that of Example I, trimethylamine,epichlorohydrin and methacrylic acid were reacted, employing a varietyof solvents. The results are shown in Table I wherein the yieldrepresents yield of Z-hydroxy- 3 methacrylyloxypropyltrimethylamrnoniumchloride based on the trimethylamine charged.

Example III By a procedure similar to that of Example I a series ofreactions employing varying molar ratios of epichlorohydrin,trimethylamine and methacrylic acid was conducted. The results are shownin Tabe II, wherein the yield represents yield of 2 hydroxy 3methacrylyloxypropyltrimethylammonium chloride based on the aminecharged. The solvent in all cases was tert-hutyl alcohol, and eachreaction mixture was heated at 60 C. for 48 hours with the exception ofExperiment 4 wherein the reaction mixture was heated at 60 C. for 6hours and then at 75 C. for 24 hours.

TABLE II Experiment 1 2 3 4 Tn'rnethylamine, moles/100 g. solution.0.179 0. 168 0.206 0. 186 Methacrylic acid, moles/mole amine. 1.151.03 1. 28 Epichlorohydrin, moles/mole amine- 1. 35 0. 95 1. 28Conversion of trimethylamine 100 55 85 Yield, percent 46 83 24 79 Whendimethyllaurylamine is reacted with acrylic acid and epibromohydrin inisopropanol solution, the molar ratio of reactants being -O.7:1:1, agood yield of 2-hydroxy 3 acrylyloxypropyldirnethyllaurylammoniumbromide is obtained.

6 f Example V 1 When the prodcedure of Exampe I'is-repeated, except thatan equivalent amount of crotonicacid is employedis place of themethacrylic'acid, a good yield of Z-hydroxy- 3crotonyloxypropyltrimethylammonium' chloride is obtained. v l

' Example' VI Several experiments were conducted -by procedures similarto that of Example 1,, except that other alcohol solvents were employedand the :2 l 1ydroxy 3v methacrylyloxypropyltrimethylammonium chloridewas obtained by cooling the product mixture at -18 C. for 24 hoursbefore filtration. The reaction mixture had been maintained at 60 C. for48 hours. The results are shown I claim as my invention:

1. The process of producing2-hydroxy-3-alkenoyloxypropyltrialkylammonium halide by intimatelycontacting (a) acyclic hydrocarbon 'monoalkene monocarboxylic acid offrom 3 to 8 carbon atoms;

('b) epihalohydrin wherein the halogen is halogen of atomic number from17 to 35, the molar ratio of epihalihydrin to said monocarboxylic acidbeing from about 3 :1 to about 1:3, and

(c) an amount greater than about 0.5 mole per mole of limiting otherreactant but less than stoichiometric of trialkylamine wherein eachalkyl independently is alkyl of from -1 to 20 carbon atoms; inliquidphase solution in inert polar solvent, at a temperature from about30 C. to about 125 C.

2. The process of claim 1 wherein the monocarboxylic acid is a-(nontomono-alkyDacrylic acid wherein any alkyl is alkyl of from 1 to 5 carbonatoms, and said inert polar solvent is dito trihydrocarbyl carbinol of 3to 10 carbon atoms.

3. The process of claim 2 wherein the epihalohydrin is epichlorohydrin.

4. The process of claim 3 wherein the amine is dimethylalkylaminewherein the alkyl is alkyl of from 1 to 20 carbon atoms present in anamount from about 0.5 mole 0t about 0.95 mole per mole of limiting otherreactant, and the dito trihydrocarbyl carbinol is dito trialkylcarbinol.

5. The process of claim 4 wherein the amine is trimethylamine.

6. The process of claim 4. wherein the monocarboxylic acid is acrylicacid or methacrylic acid, the dito trialkyl carbinol is a dito trialkylcarbinol of from 3 to 4 carbon atoms, and said contacting is conductedin the presence of from about 0.001 to about 5 molar percent based onsaid monocarboxylic acid of a polymerization inhibitor having no activehydrogen atoms and at a temperature from about 50 C to about C.

7. The process of claim 6 wherein the amine is trimethylamine.

8. The process of claim 7 wherein the acid is methacrylic acid and themolar ratio of epichlorohydrin to said methacrylic acid is from about1.5 :1 to about 1:15.

9. The process of claim 8 wherein the carbinol is secbutyl alcohol.

10. The process of claim 8 wherein the carbinol is isopropyl alcohol.

11. The process of claim 6 wherein the acid is acrylic acid.

(References on following page) Referencs Cited 3,075,999 1/1963 June efal 260-348.6 UNITED STATES PATENTS 3,170,901 2/1965 Melamed et a1.260-486 XR 3/1937 stfaub et a1 6 3,272,712 9/1966 Kalopissis et a1.260404 10/1949 Caldwell 260-486 6 OTHER REFERENCES 10/19 50 Dorough260-348 1/1951 Edwards 260 348 Kakvlchu et a1.: Chenucal Abstracts, vol.61: 777 (g), 4/1951 Oli n 260-567.6 July 1964- 'f g LORRAINE A.WEINBERGER, Primary Examiner. 1/1959 shokal et a1. 260-408 A. P.HALLUIN, Assistant Examiner.

